Generally, cathode ray tubes are sealed in a high vacuum in order to facilitate the movement of free electrons and in order to improve withstand voltage characteristics of the tubes. If foreign matter such as dust remains inside the tubes, the discharge rate increases and sharp pictures cannot be obtained due to scattering of electron beams. Accordingly, any dust in cathode ray tubes should be completely removed before the electron gun is inserted and before the tubes are sealed.
A conventional nozzle for cleaning dust from cathode ray tubes is shown in FIG. 1. This conventional nozzle is made in such a manner that one or more holes 2b communicating with hollow part 2a are formed near the end of thin and long pipe 2. This hollow part 2a extends axially in the direction of the pipe's length.
To remove dust in cathode ray tube 30 with the conventional dust cleaning nozzle 1, the nozzle 1 is inserted inside cathode ray tube 30 through neck 30a. After that, dust-free compressed-air is ejected into cathode ray tube 30 via hollow part 2a and through hole 2b of the nozzle 1. Nozzle 1 is simultaneously revolved to blow foreign matter stuck to the inner face of the cathode ray tube, the shadow mask, the frame and/or the inner shield out neck 30a and from the tube.
With the conventional nozzle 1, however, all of a high pressure is ejected only in a certain direction through holes 2b formed near the end of nozzle 1 so that only part of the inside area of the cathode ray tube is exposed to the high pressure air. Accordingly, dust cleaning is not directly performed on the entire inside area of the cathode ray tube.